There are a variety of invasive and non-invasive techniques for monitoring animals such as rodents. For example, capturing video data from a rodent's cage is one way to track movement and deduce other behaviors of the rodent. Video tracking however, has a number of significant drawbacks. The data is typically high bandwidth data and large amounts of such data can quickly accumulate. Furthermore, the quality and usefulness of video data of a rodent cage environment can depend on available lighting and sometimes requires additional lighting that may cause the rodent to modify its behavior. One additional complication of using video data is that automatic image analysis may be difficult. In order to provide automatic scene analysis, the various frames of the video data can be segmented into different objects so that movement of one or more of the objects can be tracked through a series of frames. Such segmentation and analysis can add computational complexity and overhead.
Invasive techniques for tracking some aspects of animal behavior are known such as Electroencephalographic (EEG) and Electromyographic (EMG) recordings. However, the surgery, surgery recovery, and signal scoring, among a number of other factors, limit their application to relatively small-scale studies.
Infrared radiation is a property of rodents, as well as other animals, and is capable of measurement by non-invasive means. Mammalian skin, irrespective of its color, radiates as a near perfect black-body. Similarly, the surface of an avian body also emits infrared radiation. Furthermore, the energy radiated by a black-body at room temperature is mostly infra-red, which can be captured and converted to an image using an infrared (IR) sensor.
One typical sensor for detecting movement is a passive infrared pyroelectric (PIR) sensor, such as those commonly used in security and room occupancy sensing. However, PIR sensors can only detect movement based on sudden temperature change. Furthermore, these types of sensors adapt to the environment in as little as a few minutes. Thus, the PIR sensor can become blind to a resting test subject within a relatively short period. This susceptibility can adversely impact a sensor's accuracy for detecting animal behaviors tied to low level signals such as behaviors during sleep and rest.